Enhanced creep parameters of Al-Zn alloy induced by cyclic stress reduction

Transient and steady state creep parameters, β, n and ε′s were measured for Al-12.6 wt.% Zn alloy samples at static condition and superimposed (stress reduction and frequency) in the temperature range from 443 to 503 K. The static stress was 8.86 MPa and the stress reduction σcy ranged from 1.28 to 2.99 MPa. The applied frequency ranged from 0.12 to 0.35 Hz. Increased temperature T, stress reduction σcy and frequency ν decreased the parameter n but increased both β and ε′st. The activation energy decreased with increasing σcy and/or ν due to Zn precipitation. The ratio γ showed high values relating the transient and steady creep stages.